No computers? No problem. This free worksheet generator makes printable number-systems lessons in seconds, for the day the network goes down, the room gets moved, or you need cover work in a hurry. Open the file in any web browser (Chrome, Edge, Safari or Firefox). It works completely offline, with no login, no install and no internet. Topics (pick one, or mix them): • Binary conversions (denary ↔ binary) • Binary shifts (left and right) • Binary addition with carries • Hexadecimal (hex ↔ denary ↔ binary) What you get: • A fresh, randomised double-sided A4 worksheet every time, filled edge to edge with questions • A matching answer copy for marking • A one-page cover note for whoever is covering: lesson outline, what to do with early finishers, and the key facts to read out or put on the board, so a non-specialist can run the lesson • 4-bit or 8-bit questions, with or without place-value headings • An optional GCSE challenge: overflow and lost bits • A sheet code on every page: type it in later to get the same sheet back with its answers Suitable for KS3 Computing and GCSE Computer Science (OCR J277, AQA 8525 and other boards). Made by Tom Swain, a computing teacher, as part of Swainware: a KS3 computing curriculum and GCSE revision tool. If it saves you on a stressful day, a quick review would be lovely and helps other teachers find it.